Temperature regulation

HBS3A

Homeostasis

Maintenance of constant internal environmentThis involves continually replacing substances as they are used up (eg glucose, oxygen) or continually removing substances as they build up (eg wastes)

Negative feedback systems

• Stimulus

• Receptor

• Modulator

• Effector

• Response

• Negative feedback

Negative feedback systems

• Stimulus change in conditions• Receptor detects the change• Modulator decides what to do about the

change• Effector part of the body that carries out

the response• Response change in activity• Negative feedback response alters the

stimulus in the opposite direction

Metabolism and temperatureMetabolism refers to all reactions occurring in the

bodyMetabolic rate refers to the amount or speed of

reactions in the body. It can be measured by measuring temperature, rate of oxygen consumption or rate of carbon dioxide production

Reactions produce waste heat.The more reactions that occur, the greater the

temperatureReactions rely on enzymes

Enzyme activity and temperature

Enzyme activity

Temperature

Metabolic rate and temperature

As temperature increases, metabolic rate increases

As metabolic rate increases, temperature increases

Body temperaturePoikilotherms have changing body

temperatures - the same as their environment

eg fish, amphibians, reptilesHomeotherms have constant body

temperatures regardless of the environment

eg birds, mammalsEctotherms control body temperature

by behavioureg fish, amphibians, reptilesEndotherms control body temperature

by internal mechanisms eg birds, mammals

Humans are endotherms and homeotherms

Environmental temperature

Bodytemperature

Metabolic rate

Environmental temperature

Poikilotherms

Endotherms

Homeotherms

Ectotherms

Heat production

Heat can be produced by:• Metabolism eg

• Movement

Voluntary eg Involuntary eg

Heat production

Heat can be produced by:• Metabolism eg respiration

• Movement

Voluntary eg exercise Involuntary eg shivering

Heat loss or gain

Occurs from body surfaces

Uses the processes of:

• Radiation

• Conduction

• Convection

• Evaporation

Radiation

Loss without contact

Can be increased by

Can be decreased by

Radiation

Loss without contact

Can be increased by

Increasing surface area exposure eg basking, vasodilation, taking off clothes

Can be decreased by

Decreasing surface area exposure eg huddling, vasoconstriction, putting on clothes

Conduction

Loss by contact

Can be increased by

Can be decreased by

Conduction

Loss by contact

Can be increased byIncreasing surface area exposure eg swimming

Can be decreased byDecreasing surface area exposure eg increased

insulation (eg blubber)

Convection

Loss by air movements

Can be increased by

Can be decreased by

Convection

Loss by air movements

Can be increased by

Increasing surface area exposure to wind eg sprawling, taking off clothes, turning on fan

Can be decreased by

Decreasing surface area exposure to wind eg huddling, putting on clothes

Evaporation

Loss of heat due to liquid turning to gas

Can be increased by

Can be decreased by

Evaporation

Loss of heat due to liquid turning to gas

Can be increased by sweating, panting or wetting skin

Can be decreased by reducing sweating or panting, keeping surface dry or covered with clothing

Control of body temperature

Control of heat production

Increasing or decreasing metabolic activity or movement (shivering or exercise)

Control of heat loss

Increasing or decreasing loss of heat from external or respiratory surfaces

Temperature regulation

Stimulus

Negative feedback Receptor

Response Modulator

Effector

Increased temperature

Temperature regulation

Stimulus

Negative feedback Receptor

Response Modulator

Effector

Increased temperature

Thermoreceptors

Hypothalamus in brain

Sweat glands

Increased sweating

Cool down

Temperature regulation 2

Stimulus

Negative feedback Receptor

Response Modulator

Effector

Cold

Temperature regulation 2

Stimulus

Negative feedback Receptor

Response Modulator

Effector

Thermoreceptors

Hypothalamus in brain

Cold

Muscles

Shivering

Warm up

Structural adaptations

Bare skin or reduced fur

Endomorphic body shape

Counter current exchange

Ectomorphic body shape

Physiological adaptations

Sweating

Increased breathing rateIncreased heart rate

Vasodilation

Vasoconstriction

HunchingShivering

Behavioural adaptations

Use a fan

Immersing in cold water

Seeking shadeResting during heatReduce clothes

Hot bath

Use a heater

Add clothes